Battery module and battery pack

Abstract

The invention belongs to the technical field of batteries, and discloses a battery module and a battery pack, the battery module comprises a piece and a plurality of single batteries, each single battery comprises a pole group, a first cover plate module, a second cover plate module and a shell body with openings in two sides, the first cover plate module and the second cover plate module are respectively arranged at the opening of the shell body to form an accommodating cavity for accommodating a pole group, and are respectively provided with a pole terminal welded with a bar; the effective area when the bar and each pole terminal are welded is determined according to the following formula: # imgabs0 #, so that when the lower limit value of the effective area when the bar and each pole terminal are welded is obtained, only the space size of the accommodating cavity is needed, and the charge-discharge rate A of the single battery and the capacity coefficient delta of the single battery are combined; the capacity of the single battery does not need to be calculated, so that parameters needing to be calculated are reduced, the calculation difficulty is reduced, the calculation speed is increased, and the calculation period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a battery module and a battery pack. Background Art

[0002] Lithium-ion power batteries are a new type of high-energy battery based on the movement of lithium ions between the positive and negative electrodes. During charging, lithium ions are deintercalated from the positive electrode and embedded in the negative electrode through the electrolyte; during discharging, on the contrary, lithium ions are deintercalated from the negative electrode and return to the positive electrode to form a current for device use. Due to the advantages of high energy, high battery voltage, wide operating temperature range, long storage life, etc. of lithium-ion power batteries, their application fields are very extensive, including electric vehicles, energy storage systems, military equipment, etc. With continuous development, various different types of lithium-ion power batteries have emerged, such as blade batteries, square shell batteries, or large cylindrical batteries, etc.

[0003] Among them, the bus bar is welded to the pole terminal on multiple single cells to form a battery module with a higher capacity. The effective welding area of the bus bar welded to the pole terminal needs to meet the overcurrent requirement of the single cell. Otherwise, overheating will occur at the weld mark, which will affect the cycle performance of the battery and require a higher cooling level in the module, which is not conducive to cost reduction.

[0004] When calculating the effective area during the welding of the bus bar and the pole terminal in the battery module, it is necessary to rely on the capacity of the single cell for calculation. However, the capacity calculation of the existing single cell is very cumbersome and requires calculating multiple parameters, such as the gram capacity of the material, the compaction density, the areal density, the proportion of active material, the coating area of the electrode sheet, etc., resulting in a greater difficulty in calculating the effective area during the welding of the bus bar and the pole terminal in the battery module and a long calculation cycle. Summary of the Invention

[0005] The purpose of the present invention is to provide a battery module and a battery pack with small calculation difficulty and short calculation cycle.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, a battery module is provided. The battery module includes a bus bar and multiple single cells. Each single cell includes a pole group, a first cover module, a second cover module, and a housing body with double-sided openings. The first cover module and the second cover module are respectively arranged at the openings of the housing body to form a receiving cavity for accommodating the pole group. Pole terminals for welding with the bus bar are provided on both the first cover module and the second cover module. The effective area when the bus bar is welded to each pole terminal is determined according to the following formula:

[0008] In the formula:

[0009] S is the effective area when the bus bar is welded to the terminal post, with the unit of mm 2 ;

[0010] U is the spatial dimension of the accommodation cavity along the first direction, with the unit of mm;

[0011] V is the spatial dimension of the accommodation cavity along the second direction, with the unit of mm;

[0012] W is the spatial dimension of the accommodation cavity along the third direction, with the unit of mm;

[0013] x is the gap coefficient of the electrode group along the first direction, with the unit of mm;

[0014] y is the gap coefficient of the electrode group along the second direction, with the unit of mm;

[0015] δ is the capacity coefficient of the single cell, with the unit of Ah / mm 3 ;

[0016] A is the charge and discharge rate of the single cell;

[0017] 7 is the overcurrent coefficient for the welding of the bus bar to the terminal post, with the unit of Ah / mm 2 .

[0018] Optionally, the first cover module includes a first surface facing away from the electrode group, a second surface in contact with the electrode group, and a third surface in contact with the housing body. The second cover module includes a fourth surface facing away from the electrode group, a fifth surface in contact with the electrode group, and a sixth surface in contact with the housing body. The spatial dimension U of the accommodation cavity along the first direction is determined according to the following formula: U = L + b1 + b2 - a1 - a2;

[0019] In the formula:

[0020] L is the dimension of the housing body along the first direction, with the unit of mm;

[0021] a1 is the spacing dimension between the first surface and the second surface along the first direction, with the unit of mm;

[0022] b1 is the spacing dimension between the first surface and the third surface along the first direction, with the unit of mm;

[0023] a2 is the spacing dimension between the fourth surface and the fifth surface along the first direction, with the unit of mm;

[0024] b2 is the spacing dimension between the fourth surface and the sixth surface along the first direction, with the unit of mm.

[0025] Optionally, the housing body includes a first wall surface and a fourth wall surface that are oppositely disposed along the second direction, and the spatial dimension V of the accommodation cavity along the second direction is determined according to the following formula: V = H - t1 - t4;

[0026] In the formula:

[0027] H is the dimension of the housing body along the second direction, in mm;

[0028] t1 is the thickness dimension of the first wall surface, in mm;

[0029] t4 is the thickness dimension of the fourth wall surface, in mm.

[0030] Optionally, the housing body includes a second wall surface and a third wall surface that are oppositely disposed along the third direction, and the spatial dimension W of the accommodation cavity along the third direction is determined according to the following formula: W = T - t2 - t3;

[0031] In the formula:

[0032] T is the dimension of the housing body along the third direction, in mm;

[0033] t2 is the thickness dimension of the second wall surface, in mm;

[0034] t3 is the thickness dimension of the third wall surface, in mm.

[0035] Optionally, the gap coefficient x of the electrode group along the first direction satisfies 8 mm ≤ x ≤ 12 mm.

[0036] Optionally, the gap coefficient y of the electrode group along the second direction satisfies 6 mm ≤ y ≤ 9 mm.

[0037] Optionally, in the lithium iron phosphate system, the capacity coefficient δ of the single battery satisfies 1.12×10 -4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 .

[0038] Optionally, in the ternary system, the capacity coefficient δ of the single battery satisfies 1.50×10 -4 Ah / mm 3 ≤ δ ≤ 3.35×10 -4 Ah / mm 3 .

[0039] Optionally, the distance dimension b1 between the first surface and the third surface along the first direction satisfies b1 ≥ 0.5 mm;

[0040] And / or, the fourth surface and the sixth surface have a spacing dimension b2 along the first direction, satisfying b2≥0.5mm.

[0041] On the other hand, a battery pack is also provided. The battery pack includes an electrical connection structure and a plurality of battery modules as described in any one of the above. The plurality of battery modules are arranged in sequence and connected, and the electrical connection structure is electrically connected to the plurality of battery modules.

[0042] Advantages of the present invention:

[0043] The present invention provides a battery module. When calculating the lower limit value of the effective area during the welding of the tab and the pole terminal in the battery module through the formula only the spatial dimensions of the accommodation cavity are required, that is, the spatial dimension U of the accommodation cavity along the first direction, the spatial dimension V of the accommodation cavity along the second direction, and the spatial dimension W of the accommodation cavity along the third direction, combined with the charge and discharge rate A of the single battery and the capacity coefficient δ of the single battery. There is no need to calculate the capacity of the single battery separately, thereby reducing the parameters to be calculated, lowering the calculation difficulty, improving the calculation speed, and shortening the calculation cycle.

[0044] The present invention also provides a battery pack. By applying the above battery module, with the improvement of the calculation speed, the waiting time can be reduced during the production process of the battery pack, thereby improving the overall production efficiency. Description of the drawings

[0045] Figure 1 is a schematic structural diagram of the welding of the single battery and the tab provided by the present invention;

[0046] Figure 2 is Figure 1 an enlarged structural view of part I in

[0047] Figure 3 is an exploded structural view of the single battery provided by the present invention;

[0048] Figure 4 is a cross-sectional structural view of the single battery provided by the present invention;

[0049] Figure 5 is Figure 4 an enlarged structural view of part II in

[0050] Figure 6 is Figure 4 an enlarged structural view of part III in

[0051] Figure 7 is a three-dimensional structural view of the housing body in the single battery provided by the present invention;

[0052] Figure 8It is a plan view of the housing body of the single battery provided by the present invention along the first direction.

[0053] In the figure:

[0054] 100, bar-shaped weld mark; 200, circular weld mark; 300, square weld mark;

[0055] 1, tab;

[0056] 2, single battery; 21, electrode group; 22, first cover module; 221, first surface; 222, second surface; 223, third surface; 224, first cover body; 2241, first closed part; 2242, first insertion part; 225, first lower insulating part; 23, second cover module; 231, fourth surface; 232, fifth surface; 233, sixth surface; 234, second cover body; 2341, second closed part; 2342, second insertion part; 235, second lower insulating part; 24, housing body; 241, first wall surface; 242, second wall surface; 243, third wall surface; 244, fourth wall surface; 25, accommodation cavity. Detailed implementation manners

[0057] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the convenience of description, only parts related to the present invention rather than all structures are shown in the drawings.

[0058] In the description of the present invention, unless otherwise clearly defined and limited, the terms "connected", "connected to", and "fixed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact of the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features between them. Moreover, the first feature being "above", "above and to the right", and "above and on" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "below and to the left", and "below and on" the second feature includes the first feature being directly below and obliquely below the second feature, or simply indicating that the first feature has a lower horizontal height than the second feature.

[0060] In the description of this embodiment, the orientation or positional relationships such as "upper", "lower", "right", etc. are based on the orientation or positional relationships shown in the drawings. They are only for the convenience of description and simplifying the operations, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0061] When calculating the effective area during the welding of the tab in the battery module to the pole terminal, it is necessary to rely on the capacity of the single battery for calculation. However, the calculation of the capacity of the existing single battery is very cumbersome and requires calculating multiple parameters, such as the gram capacity of the material, the compaction density, the areal density, the proportion of the active material, the coating area of the electrode sheet, etc. As a result, the calculation of the effective area during the welding of the tab in the battery module to the pole terminal is difficult and the calculation period is long.

[0062] In order to reduce the calculation difficulty and improve the calculation speed, this embodiment provides a battery module.

[0063] As Figures 1 to 8 shown, the battery module includes a tab 1 and a plurality of single batteries 2. Each single battery 2 includes a pole group 21, a first cover module 22, a second cover module 23, and a housing body 24 with double-sided openings. The first cover module 22 and the second cover module 23 are respectively arranged at the openings of the housing body 24 to form a receiving cavity 25 for accommodating the pole group 21. Pole terminals for welding with the tab 1 are provided on both the first cover module 22 and the second cover module 23. The effective area when the tab 1 is welded to each pole terminal is determined according to the following formula:

[0064] In the formula:

[0065] S is the effective area when the tab 1 is welded to the pole terminal, with the unit of mm 2 ;

[0066] U is the spatial dimension of the receiving cavity 25 along the first direction, with the unit of mm;

[0067] V is the spatial dimension of the receiving cavity 25 along the second direction, with the unit of mm;

[0068] W is the spatial dimension of the receiving cavity 25 along the third direction, with the unit of mm;

[0069] x is the gap coefficient of the pole group 21 along the first direction, with the unit of mm;

[0070] y is the gap coefficient of the pole group 21 along the second direction, with the unit of mm;

[0071] δ is the capacity coefficient of the single battery 2, with the unit of Ah / mm 3 ;

[0072] A is the charge and discharge rate of the single battery 2;

[0073] 7 is the overcurrent coefficient for the welding of the bus bar 1 and the terminal post, with the unit of Ah / mm 2 .

[0074] When calculating the lower limit value of the effective area during the welding of the bus bar 1 and the terminal post in the battery module through the formula , only the space dimensions of the accommodation cavity 25 are needed, that is, the space dimension U of the accommodation cavity 25 in the first direction, the space dimension V of the accommodation cavity 25 in the second direction, and the space dimension W of the accommodation cavity 25 in the third direction. Combining with the charge and discharge rate A of the single battery 2 and the capacity coefficient δ of the single battery 2 is sufficient, without the need for separate calculation of the capacity of the single battery 2. Thereby, the parameters to be calculated are reduced, the calculation difficulty is lowered, the calculation speed is increased, and the calculation cycle is shortened.

[0075] In this embodiment, since the charge and discharge rates A of batteries with different specifications and sizes are different, when calculating the charge and discharge rate A of the single battery 2, first determine the time Z required for the current single battery 2 to be fully charged, with the unit of min; secondly, calculate according to the formula A = 60min / Z to obtain the charge and discharge rate A of the current single battery 2.

[0076] Among them, since the material of the bus bar 1 is aluminum, and the bus bar 1 and the terminal post are welded outside the single battery 2, according to the national standard, the overcurrent coefficient in this calculation formula is determined to be 7. In addition, as Figure 2 shown, the welding track of the bus bar 1 and the terminal post can be freely set to form a strip-shaped weld mark 100, a circular weld mark 200, a square weld mark 300, etc., as long as the effective area after welding meets the calculation requirements.

[0077] Optionally, as Figures 4 to 7 shown, the first cover module 22 includes a first surface 221 facing away from the electrode group 21, a second surface 222 in contact with the electrode group 21, and a third surface 223 in contact with the housing body 24. The second cover module 23 includes a fourth surface 231 facing away from the electrode group 21, a fifth surface 232 in contact with the electrode group 21, and a sixth surface 233 in contact with the housing body 24. The space dimension U of the accommodation cavity 25 in the first direction is determined according to the following formula: U = L + b1 + b2 - a1 - a2;

[0078] In the formula:

[0079] L is the dimension of the housing body 24 in the first direction, with the unit of mm;

[0080] a1 is the spacing dimension between the first surface 221 and the second surface 222 in the first direction, with the unit of mm;

[0081] b1 is the spacing dimension between the first surface 221 and the third surface 223 in the first direction, with the unit of mm;

[0082] a2 is the spacing dimension between the fourth surface 231 and the fifth surface 232 in the first direction, with the unit of mm;

[0083] b2 is the spacing dimension between the fourth surface 231 and the sixth surface 233 in the first direction, with the unit of mm.

[0084] By determining the dimension L of the housing body 24 in the first direction, the spacing dimension a1 between the first surface 221 and the second surface 222 of the first cover module 22 in the first direction, the spacing dimension b1 between the first surface 221 and the third surface 223 of the first cover module 22 in the first direction, the spacing dimension a2 between the fourth surface 231 and the fifth surface 232 of the second cover module 23 in the first direction, and the spacing dimension b2 between the fourth surface 231 and the sixth surface 233 in the first direction, the spatial dimension U of the accommodation cavity 25 in the first direction can be obtained more intuitively through the above structural parameters, reducing the difficulty of determining the spatial dimension U of the accommodation cavity 25 in the first direction.

[0085] In this embodiment, the first cover module 22 includes a first cover body 224, and the first cover body 224 includes a first closing portion 2241 and a first insertion portion 2242. The surface of the first closing portion 2241 facing the electrode group 21 bulges in the direction close to the electrode group 21 to form the first insertion portion 2242. The first insertion portion 2242 is inserted into the housing body 24. The first closing portion 2241 is used to close the open end of the housing body 24. The first surface 221 is the surface of the first closing portion 2241 facing away from the electrode group 21, and the surface of the first closing portion 2241 in contact with the housing body 24 is the third surface 223. The first cover module 22 further includes a first lower insulating member 225 located inside the housing body 24 and used to abut against the electrode group 21. The surface of the first lower insulating member 225 in contact with the electrode group 21 is the second surface 222.

[0086] In this embodiment, the second cover module 23 includes a second cover body 234, and the second cover body 234 includes a second closing portion 2341 and a second insertion portion 2342. The surface of the second closing portion 2341 facing the electrode group 21 protrudes in the direction close to the electrode group 21 to form the second insertion portion 2342. The second insertion portion 2342 is inserted into the housing body 24. The second closing portion 2341 is used to close the opening of the housing body 24. Among them, the fourth surface 231 is the surface of the second closing portion 2341 facing away from the electrode group 21, and the surface of the second closing portion 2341 in contact with the housing body 24 is the sixth surface 233. The second cover module 23 further includes a second lower insulating member 235 located inside the housing body 24 and used to abut against the electrode group 21. The surface of the second lower insulating member 235 in contact with the electrode group 21 is the fifth surface 232.

[0087] Optionally, as Figure 7 and Figure 8 shown, the housing body 24 includes a first wall surface 241 and a fourth wall surface 244 arranged oppositely along the second direction. The spatial dimension V of the accommodation cavity 25 along the second direction is determined according to the following formula: V = H - t1 - t4;

[0088] In the formula:

[0089] H is the dimension of the housing body 24 along the second direction, with the unit of mm;

[0090] t1 is the thickness dimension of the first wall surface 241, with the unit of mm;

[0091] t4 is the thickness dimension of the fourth wall surface 244, with the unit of mm.

[0092] By determining the dimension H of the housing body 24 along the second direction, the thickness dimension t1 of the first wall surface 241 of the housing body 24, and the thickness dimension t4 of the fourth wall surface 244 of the housing body 24, the dimension V of the accommodation cavity 25 along the second direction can be more intuitively calculated through the above structural parameters, reducing the difficulty of obtaining the spatial dimension V of the accommodation cavity 25 along the second direction.

[0093] Optionally, as Figure 7 and Figure 8 shown, the housing body 24 includes a second wall surface 242 and a third wall surface 243 arranged oppositely along the third direction. The spatial dimension W of the accommodation cavity 25 along the third direction is determined according to the following formula: W = T - t2 - t3;

[0094] In the formula:

[0095] T is the dimension of the housing body 24 along the third direction, with the unit of mm;

[0096] t2 is the thickness dimension of the second wall 242, with the unit of mm;

[0097] t3 is the thickness dimension of the third wall 243, with the unit of mm.

[0098] By determining the dimension T of the housing body 24 along the third direction, the wall thickness dimension t2 of the second wall 242 of the housing body 24, and the wall thickness dimension t3 of the third wall 243 of the housing body 24, the dimension W of the accommodation cavity 25 along the third direction can be more intuitively calculated through the above structural parameters, reducing the difficulty of obtaining the spatial dimension W of the accommodation cavity 25 along the third direction.

[0099] Among them, the thicknesses of the first wall 241, the second wall 242, the third wall 243, and the fourth wall 244 constituting the housing body 24 can be the same or different. The forming of the housing body 24 generally includes two processes: aluminum plate bending and welding, and aluminum rod extrusion. The housing body 24 with equal wall thickness generally adopts the aluminum plate bending and laser welding process, and the housing body 24 with unequal wall thickness generally adopts the extrusion process. In this embodiment, the housing body 24 with equal wall thickness of bending laser welding is preferably selected, that is, t1 = t2 = t3 = t4.

[0100] Since the spatial dimension U of the accommodation cavity 25 along the first direction, the spatial dimension V of the accommodation cavity 25 along the second direction, and the spatial dimension W of the accommodation cavity 25 along the third direction can be calculated through the structural dimensions of the components in the housing body 24, the first cover module 22, and the second cover module 23, the formula for calculating the effective area S when the bus bar 1 is welded to the pole terminal can be deformed into Compared with calculating using the spatial dimensions of each direction of the accommodation cavity 25, the calculation difficulty is lower and the calculation speed is faster.

[0101] Optionally, the gap coefficient x of the electrode group 21 along the first direction satisfies 8mm ≤ x ≤ 12mm. By limiting the gap coefficient x of the electrode group 21 along the first direction to satisfy 8mm ≤ x ≤ 12mm, on the one hand, it avoids being too small, resulting in insufficient space for the bending of the tab, causing the tab to be crushed, and on the other hand, it avoids being too large, resulting in a gap between the electrode group 21 and the inner wall of the housing body 24 even after charging and expansion, causing the electrode group 21 to move and strain the tab.

[0102] In this embodiment, the gap coefficient x of the electrode group 21 along the first direction is the length of the Overhang of the separator and the negative electrode + the length of the Overhang of the negative electrode and the positive electrode. The length of the Overhang of the separator and the negative electrode refers to the distance that the two sides of the separator exceed the two sides of the negative electrode along the first direction, and the length of the Overhang of the negative electrode and the positive electrode refers to the distance that the two sides of the negative electrode exceed the two sides of the positive electrode along the first direction.

[0103] To verify the influence of the gap coefficient x of the electrode group 21 in the first direction on the insertion of the electrode group 21 into the shell, as shown in Table 1, three sets of examples and two sets of comparative examples are provided for verification.

[0104] Table 1

[0105]

[0106] As can be seen from the above table, when the gap coefficient x of the electrode group 21 in the first direction meets the range requirement of 8 mm ≤ x ≤ 12 mm, the insertion into the shell is smooth. When the gap coefficient x of the electrode group 21 in the first direction is less than the minimum value of the range of 8 mm ≤ x ≤ 12 mm, it cannot provide enough space for the bending of the tab, resulting in the tab being crushed. When the gap coefficient x of the electrode group 21 in the first direction is greater than the maximum value of the range of 8 mm ≤ x ≤ 12 mm, the electrode group 21 moves around, resulting in the tab being strained.

[0107] Optionally, the gap coefficient y of the electrode group 21 in the second direction satisfies 6 mm ≤ y ≤ 9 mm. By limiting the gap coefficient y of the electrode group 21 in the second direction to satisfy 6 mm ≤ y ≤ 9 mm, on the one hand, it avoids being too small, which may cause difficulties in inserting the electrode group 21 into the shell and result in scratching of the electrode group 21. On the other hand, it avoids being too large, which may cause a gap between the electrode group 21 and the inner wall of the outer shell body 24 even after charging and expansion, resulting in the electrode group 21 moving around and straining the tab.

[0108] In this embodiment, the gap coefficient y of the electrode group 21 in the second direction is the insertion gap of the electrode group 21 + the height of the overhang of the separator from the negative electrode sheet + the height of the overhang of the negative electrode sheet from the positive electrode sheet, where the insertion gap of the electrode group 21 is the distance between the two side edges of the electrode group 21 in the second direction and the inner surfaces of the opposite first wall surface 241 and the fourth wall surface 244; the height of the overhang of the separator from the negative electrode sheet refers to the distance of the parts where the two sides of the separator exceed the two sides of the negative electrode sheet in the second direction; the height of the overhang of the negative electrode sheet from the positive electrode sheet refers to the distance of the parts where the two sides of the negative electrode sheet exceed the two sides of the positive electrode sheet in the second direction.

[0109] To verify the influence of the gap coefficient y of the electrode group 21 in the second direction on the insertion of the electrode group 21 into the shell, as shown in Table 2, three sets of examples and two sets of comparative examples are provided for verification.

[0110] Table 2

[0111]

[0112] As can be seen from the above table, when the gap coefficient y of the electrode group 21 in the second direction meets the range requirement of 6 mm ≤ y ≤ 9 mm, the insertion into the shell is smooth. When the gap coefficient y of the electrode group 21 in the second direction is less than the minimum value of the range of 6 mm ≤ y ≤ 9 mm, the gap during the insertion of the electrode group 21 is too small, resulting in scratches on the electrode group 21. When the gap coefficient y of the electrode group 21 in the second direction is greater than the maximum value of the range of 6 mm ≤ y ≤ 9 mm, the electrode group 21 moves around, resulting in damage to the tab.

[0113] Optionally, in the lithium iron phosphate system, the capacity coefficient δ of the single cell 2 satisfies 1.12×10 -4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 . By limiting the capacity coefficient δ of the single cell 2 in the lithium iron phosphate system to satisfy 1.12×10 - 4 Ah / mm 3 ≤ δ ≤ 2.47×10 -4 Ah / mm 3 , the effective area S obtained by calculation for welding the tab 1 and the terminal of the pole column is ensured to be highly targeted and accurate.

[0114] Optionally, in the ternary system, the capacity coefficient δ of the single cell 2 satisfies 1.50×10 -4 Ah / mm 3 ≤ δ ≤ 3.35×10 -4 Ah / mm 3 . By limiting the capacity coefficient δ of the single cell 2 in the ternary system to satisfy 1.50×10 - 4 Ah / mm 3 ≤ δ ≤ 3.35×10 -4 Ah / mm 3 , the effective area S obtained by calculation for welding the tab 1 and the terminal of the pole column is ensured to be highly targeted and accurate.

[0115] In this embodiment, the capacity coefficient of the single cell 2 is derived from the capacity calculation of the single cell 2. The capacity of the single cell 2 is defined as C, and the capacity C of the single cell 2 = the length of the positive electrode sheet material area × the height of the positive electrode sheet material area × the surface density of the positive electrode × the active material content × 2 × the specific capacity of the positive electrode × the number of positive electrode sheets. Among them, the units of the length and height of the positive electrode sheet material area are mm, the unit of the surface density is mg / cm 2 , the unit of the specific capacity is mAh / g, and the active material content is %, and further, the length of the positive electrode sheet material area = L + b1 + b2 - a1 - a2 - x, the height of the positive electrode sheet material area = H - t1 - t4 - y, where the assembly ratio is 89% - 91%, so it can be obtained that

[0116] Denote the in the formula as δ, so as to obtain the capacity coefficient δ of the single battery 2, where the units of each parameter in the formula are converted, that is, mm 2 is converted to cm 2 , mg is converted to g, mAh is converted to Ah, and the parameter "2" represents coating on both sides of the foil.

[0117] Among them, in this formula, the positive electrode surface density = 20 mg / cm 2 ~25 mg / cm 2 , the active substance content = 95% - 98%, the specific capacity of the positive electrode in the lithium iron phosphate system = 135 mAh / g - 155 mAh / g, the specific capacity of the positive electrode in the ternary system = 180 mAh / g - 210 mAh / g, the thickness of the positive electrode sheet = 155 um - 215 um, the thickness of the negative electrode sheet 105 um - 167 um, the thickness of the separator = 10 um - 12 um. Substitute the above data to obtain the capacity coefficient δ of the single battery 2 in the lithium iron phosphate system, that is, 1.12×10 -4 Ah / mm 3 ≤δ≤2.47×10 -4 Ah / mm 3 , and obtain the capacity coefficient δ of the single battery 2 in the ternary system, that is, 1.50×10 -4 Ah / mm 3 ≤δ≤3.35×10 -4 Ah / mm 3 .

[0118] Optionally, the distance dimension b1 between the first surface 221 and the third surface 223 along the first direction satisfies b1≥0.5 mm, preferably 0.75 mm; by limiting the distance dimension b1 between the first surface 221 and the third surface 223 along the first direction, it is avoided that the size is too small, resulting in too low structural strength and easy deformation.

[0119] The distance dimension b2 between the fourth surface 231 and the sixth surface 233 along the first direction satisfies b2≥0.5 mm, preferably 0.75 mm. By limiting the distance dimension b2 between the fourth surface 231 and the sixth surface 233 along the first direction, it is avoided that the size is too small, resulting in too low structural strength and easy deformation.

[0120] Table 3

[0121]

[0122] Limit the above parameters according to the values in Table 3 to obtain the lower limit of the effective area S when the terminal of the single cell 2 is welded to the tab 1 in different systems under the current size specification. That is, in the ternary system, the effective area S when the tab 1 is welded to the terminal of the pole is S ≮ 23.4mm 2 , in the lithium iron phosphate system, the effective area S when the tab 1 is welded to the terminal of the pole is S ≮ 17.4mm 2 .

[0123] Among them, in order to verify the rationality of the effective area S when the tab 1 is welded to the terminal of the pole obtained by calculating the above various parameters, as shown in Table 4, three groups of examples and three groups of comparative examples are selected to verify the calculation results in the ternary system, and observe the temperature conditions of the welding area between the terminal of the pole and the tab 1 under different welding mark areas.

[0124] Table 4

[0125]

[0126] As can be seen from Table 4, in the ternary system, when the effective area S when the tab 1 is welded to the terminal of the pole is greater than the lower limit of the effective area S when the tab 1 is welded to the terminal of the pole obtained by calculating the above various parameters, the temperature of its welding mark area is less than 65°C, and the performance is good. When the effective area S when the tab 1 is welded to the terminal of the pole is less than the lower limit of the effective area S when the tab 1 is welded to the terminal of the pole obtained by calculating the above various parameters, the temperature of its welding mark area exceeds 65°C, the cycle performance of the battery cell decreases, and an external cooling device needs to be added, resulting in high costs.

[0127] In this embodiment, a battery pack is further provided. The battery pack includes an electrical connection structure and a plurality of the above-mentioned battery modules. The plurality of battery modules are arranged in sequence and connected, and the electrical connection structure is electrically connected to the plurality of battery modules. By applying the above-mentioned battery module in this battery pack, with the improvement of the calculation speed, the waiting time can be reduced during the production process of the battery pack, thereby improving the overall production efficiency.

[0128] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A battery module, characterized in that: The battery module includes a bar and a plurality of single cells, each of which includes a pole group, a first cover plate module, a second cover plate module and a shell body with double-sided openings, the first cover plate module and the second cover plate module are respectively arranged at the openings of the shell body to form a receiving cavity for accommodating the pole group, the first cover plate module and the second cover plate module are both provided with pole terminals welded to the bar, and the effective area of ​​the bar when welded to each pole terminal is determined according to the following formula: Where: S is the effective area when the bar and the pole terminal are welded, in mm 2 ; U is the spatial dimension of the accommodating cavity along the first direction, in mm; V is the spatial dimension of the accommodating cavity along the second direction, in mm; W is the spatial dimension of the accommodating cavity along the third direction, in mm; x is the gap coefficient of the pole group along the first direction, in mm; y is the gap coefficient of the pole group along the second direction, in mm; δ is the capacity coefficient of the single cell, in Ah / mm 3 ; A is the charge and discharge rate of the single cell; 7 is the overcurrent coefficient of the welding between the bar and the pole terminal, in Ah / mm 2 .

2. The battery module according to claim 1, characterized in that: The first cover plate module includes a first surface away from the pole group, a second surface abutting the pole group, and a third surface abutting the shell body, the second cover plate module includes a fourth surface away from the pole group, a fifth surface abutting the pole group, and a sixth surface abutting the shell body, and the spatial dimension U of the accommodating cavity along the first direction is determined according to the following formula: U=L+b1+b2-a1-a2; Where: L is the size of the housing body along the first direction, in mm; a1 is the distance between the first surface and the second surface along the first direction, in mm; b1 is the distance between the first surface and the third surface along the first direction, in mm; a2 is the distance between the fourth surface and the fifth surface along the first direction, in mm; b2 is the distance between the fourth surface and the sixth surface along the first direction, and the unit is mm.

3. The battery module according to claim 1, characterized in that: The housing body comprises a first wall surface and a fourth wall surface which are arranged opposite to each other along the second direction, and a spatial dimension V of the accommodating cavity along the second direction is determined according to the following formula: V=H-t1-t4; Where: H is the dimension of the housing body along the second direction, in mm; t1 is the thickness of the first wall, in mm; t4 is the thickness of the fourth wall, in mm.

4. The battery module according to claim 1, characterized in that: The shell body comprises a second wall surface and a third wall surface which are arranged opposite to each other along the third direction, and a spatial dimension W of the accommodating cavity along the third direction is determined according to the following formula: W=T-t2-t3; Where: T is the dimension of the housing body along the third direction, in mm; t2 is the thickness of the second wall, in mm; t3 is the thickness of the third wall, in mm.

5. The battery module according to claim 1, characterized in that: The gap coefficient x of the pole group along the first direction satisfies 8mm≤x≤12mm.

6. The battery module according to claim 1, characterized in that: The gap coefficient y of the pole group along the second direction satisfies 6mm≤y≤9mm.

7. The battery module according to claim 1, characterized in that: In the iron-lithium system, the capacity coefficient δ of the single cell satisfies 1.12×10 -4 Ah / mm 3 ≤δ≤2.47×10 -4 Ah / mm 3 .

8. The battery module according to claim 1, characterized in that: In the ternary system, the capacity coefficient δ of the single cell satisfies 1.50×10 -4 Ah / mm 3 ≤δ≤3.35×10 -4 Ah / mm 3 .

9. The battery module according to claim 2, characterized in that: A spacing dimension b1 between the first surface and the third surface along the first direction satisfies b1≥0.5 mm; And / or, a spacing dimension b2 between the fourth surface and the sixth surface along the first direction satisfies b2 ≥ 0.5 mm.

10. A battery pack, characterized in that: The battery pack comprises an electrical connection structure and a plurality of battery modules as described in any one of claims 1 to 9, wherein the plurality of battery modules are arranged in sequence and connected to each other, and the electrical connection structure is electrically connected to the plurality of battery modules.

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